期刊
ACS NANO
卷 13, 期 6, 页码 6363-6371出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsnano.9b02744
关键词
TERS; tunneling plasmons; confined light; Stark effect; functionalized tips
类别
资金
- National Science Foundation through the Center for Chemistry at the Space-Time Limit [CHE-1414466]
Tip-enhanced Raman scattering (TERS) with a cobalt tetraphenylporphyrin (CoTPP)-terminated silver tip is used to obtain ion-selective, atomically resolved images of an insulating Cu2N monolayer grown on Cu(100). Ion selective images are obtained through vibrational frequency shift maps using CoTPP vibrations with oppositely signed Stark tuning rates (STR). The images allow a quantitative analysis of the electrostatic field of the ionic lattice using in situ calibrated STRs. Both intensity and Stark shift maps yield atomically resolved images in the tunneling regime of plasmons. We show that the CoTPP is bonded to the Ag tip through its central Co atom, whereby TERS taps into intramolecular currents and polarizations. The bias dependence of vibrational line intensities shows diode-like response with opposite polarity for current carrying modes of opposite polarization phase. The phase sensitive detection of vibrational lines and their voltage gating is explained in terms of distinct field- and phototunneling current-driven Raman, offering an alternate paradigm for the long-sought optoelectronic rectifier in molecular electronics.
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